The present invention relates generally to an agricultural grinding and mixing implement and more particularly to a mixing blade used with a cylindrical, flat bottomed mixer tank.
In order to provide an improved mixer-guide having a lower center of gravity and greater volume, and avoid bridging of material during the mixing process, an upright cylindrical tank having a substantially flat bottom has been utilized in place of the conventional tanks with a conical bottom. Such a flat-bottomed mixing apparatus is illustrated in U.S. Pat. No. 3,667,734 to Skromme et al., issued June 6, 1972, and includes a center mixing auger operable within a vertical housing mounted concentrically within the tank. That design utilizes a mixing blade which is fixed to the bottom of the auger and sweeps the tank bottom as the auger rotates. The mixing blade, in conjunction with the mixing auger, agitates and thoroughly mixes the materials in the tank. Grinder-mixers with that tank design are capable of circulating and mixing roughage material that might otherwise cause bridging in the throat of a conventional tank with a conical bottom.
The mixing blade commonly used with a flat-bottomed tank is attached to the auger with only a fraction of an inch clearance provided between the tank floor and the bottom blade surface. The blade extends outwardly to within a fraction of an inch of the inside surface of the vertical walls of the tank, and a circumferential guide is provided near the outer end of the blade to constrain it near to the floor. The blade sweeps across two openings in the tank bottom, one for loading and one for unloading. Even though the leading edge of the blade is beveled to a sharp edge, coarsely ground material such as hay can be trapped between the edges of the openings and the blade and cause excessive impact loads as the blade sweeps over the openings. This type of load is especially severe across the discharge hole located near the vertical wall of the tank, since the material tends to be more concentrated and packed near the end of the blade. The load caused by the outer tip of the blade passing through the concentrated and packed material greatly increases the torque requirements. Also, roughage material cannot slide off the free end of the blade because of the small amount of clearance between the blade end and the tank wall thus adding to the load. These added loads can eventually damage the blade, mixing auger and drive train parts.